1. Field of the Invention
This invention relates to master cylinders for vehicle braking systems, and in particular to a master cylinder which comprises a body with an axial bore open at the rear end of the body, a reservoir chamber, a transverse port in the body opening into the bore and positioned rearwardly of the reservoir chamber, and a passage communicating said reservoir chamber with said transverse port.
2. Description of the Prior Art
A master cylinder of the above form is proposed in our copending British patent application No. 8018215 (Publication No. 2052656 and U.S. Ser. No. 154,798, filed May 30, 1980 and now abandoned) and the advantage of this construction is that it allows the reservoir to be located at the forward end of the body, whereby the rear end of the master cylinder can be received within an actuating servo-booster and an overall space saving achieved.
In the master cylinders disclosed in the aforementioned Application the transverse port which is normally open to a pressure chamber defined in the bore of the master cylinder body, communicates with the reservoir chamber through a longitudinal passageway extending through the wall of the body parallel to the bore axis, the passageway extending forwardly from an internal shoulder formed in the bore to the reservoir chamber and intersecting the transverse port.
It has now been found that the longitudinal passageway is more difficult to machine through the body wall than had been anticipated. The main problems encountered are difficulty in maintaining the straightness of the passageway over the necessary length; difficulty in ensuring correct fluid connection between reservoir chamber and transverse port; and weakening of the wall of the master cylinder body. Although the last mentioned problem could be avoided by making the body wall thicker it would be contrary to the main objectives of minimising space and weight.